Anne Whitaker, who joined Sanofi three years ago to run its North America pharmaceutical operations and help the drug maker push into lucrative markets such as diabetes, is leaving next month, according to an internal memo.

In a brief note to employees, Peter Guenter, an executive vice president for global commercial operations at Sanofi, wrote that Whitaker “played a central role in the transformation of our North American pharmaceutical business during a time of significant market evolution.”